Regular participation in out-of-school time activities is associated with benefits for children. However, children cannot reap the benefits of program participation if they do not attend programs in the first place. This brief focuses on ways in which out-of-school time programs can improve the attendance and retention of children and youth in their programs during the elementary, middle, and high school years and provides ideas for overcoming common barriers to attendance. The brief also describes an action plan that program practitioners can use to measure attendance and retention in their programs. Included in this brief is a profile of the Higher Achievement program in Washington, DC. It describes the program's mission and addresses the importance of attendance and retention to this program, barriers to attendance and retention, strategies the Higher Achievement program uses to overcome those barriers, how the program measures attendance and retention, and the evaluation strategies that the program uses. (Contains 23 endnotes.)